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HOBO MX2501 Bluetooth pH & Temperature Data Logger

Brand: Onset HOBO
Product Code: MX2501
HOBO MX2501 Bluetooth pH & Temperature Data Logger
Ex VAT £799.78 Inc VAT £959.74

Availability: In stock

SKU: MX2501

Product Description

The HOBO MX2501 pH and Temperature Data Logger is designed for long-term monitoring of pH in bodies of water including: estuaries, lakes, streams, rivers, and oceans. Leveraging Bluetooth Low Energy® (BLE) technology, the MX2501 pH Logger communicates wirelessly with the free HOBOmobile® app, making logger setup, calibration, and data offload quick and easy.

A guided pH calibration process on the free HOBOmobile app makes an otherwise complicated process easier to follow. Also view data in graphs, check the operational status of loggers, share data files and graph images, and store data in the cloud. Available for iOS devices from the App Store and for Android from the Google Play store.

This affordable and compact logger dramatically cuts the time and effort needed to collect field data, while also offering higher data resolution.

Highlighted Features

  • Rugged PVC housing for deployment in both freshwater and saltwater environments

  • Quick and easy data offload via Bluetooth Low Energy (BLE) to iOS devices (Android coming soon)!

  • Water detection system for longer battery life and less maintenance

  • Potentiometric pH electrode with plastic body, gel electrolyte, and double cloth junction

  • User-replaceable battery, pH electrode, and anti-biofouling copper guard

  • Accuracy of ±0.10 pH units within ±10°C of temperature at calibration.

NOTE: pH electrodes should always be stored in storage solution when not deployed.


Call +44 (0)1243 558270, click on the webchat box below, or fill out our contact form.

Availability: In stock

Additional Information

Additional Information


pH Sensor

Range 2.00 to 12.00 pH, -512 to 512 mV

Accuracy ±0.10 pH units within ±10°C of temperature at calibration, ±0.20 mV

Resolution 0.01 pH, 0.02 mV

Response Time 1 minute typical to 90% at constant temperature in stirred water


Temperature Sensor

Range -2° to 50°C (28.4° to 122°F)

Accuracy ±0.2°C (±0.36°F)

Resolution 0.024°C at 25°C (0.04°F at 77°F)

Response Time 7 minutes typical to 90% in stirred water



Operating Range -2° to 50°C (28.4° to 122°F) — non-freezing

Buoyancy Fresh water: 13.6 g (0.48 oz) negative / Salt water: 19.6 g (0.69 oz) negative

Waterproof To 40 m (131.2 ft)

Water Detection Water conductivity level of 100 µS/cm or greater is necessary for reliable detection of water. Deionized water or water below 100 µS/cm may not be detected.

The water conductivity circuit may not reliably detect water that has frozen around the electrodes, i.e. below 0°C (32°F).

Radio Power 1 mW (0 dBm)

Transmission Range Approximately 30.5 m (100 ft) line-of-sight in air

Wireless Data Standard Bluetooth Low Energy (Bluetooth Smart)

Logging Rate 1 second to 18 hours

Logging Modes Fixed interval (normal, statistics) or burst

Memory Modes Wrap when full or stop when full

Start Modes Immediate, push button, date & time, or next interval

Stop Modes When memory is full, push button, date & time, or after a set logging period

Time Accuracy ±1 minute per month 0° to 50°C (32° to 122°F)

Battery Type One AA 1.5 Volt, user-replaceable

Battery Life

1 year typical at 25°C (77°F) with logging interval of 1 minute and Bluetooth Always On selected in software.

2 years typical at 25°C (77°F) with logging interval of 1 minute and Bluetooth Off Water Detect enabled in software.

3 years typical at 25°C (77°F) with logging interval of 1 minute and Bluetooth Always Off selected in software.

Faster logging intervals and statistics sampling intervals, burst logging, remaining connected with the app, excessive downloads, and paging may impact battery life.
pH Electrode Life 6 months

Memory 152 KB (43,300 measurements, maximum)

Full Memory Download Time Approximately 60 seconds; may take longer the farther the mobile device is from the logger

Dimensions 22.86 x 4.27 cm (9.0 x 1.68 inches)

Weight 268.2 g (9.46 oz)

Wetted Materials

Logger: PVC housing and sensor end cap, polycarbonate closure caps and mounting end cap with a TPE switch

pH electrode: plastic-bodied with Pellon® junctions and gel electrolyte, glass pH sensor bulb

Environmental Rating IP68

CE Compliant The CE Marking identifies this product as complying with all relevant directives in the European Union (EU).

Country of Manufacture United States
Maximum Temperature 50°C
Minimum Temperature -2°C
Tolerance 0.024°C at 25°C
Typical Applications Datalogging, Environmental (Outdoor), Field Research, Research, Temperature, Water Quality
Data Available By Bluetooth
Measurements pH, Temperature